Several techniques are in use to measure the flow of blood within a patient's vasculature. Doppler ultrasound and dilution techniques can be used to study blood flow in vessels, and these devices are common. Hot wire anemometry has been proposed to measure blood flow as well.
The measurement of blood flow in a coronary artery is especially difficult due to the size and location of the vessel. For example, the measurement device must have a very small diameter so that the vessel under study is not occluded during the measurement. Occlusion will distort the flow measurement and can cause ischemia. It is also important that the flow measurement device generate a reproducible and accurate measure of blood flow as a function of time so that the pulsatile nature of the blood flow is revealed. Typically, this type of information is used by the physician to assess the efficacy of an angioplasty procedure.
The ideal flow measurement apparatus would be accurate, small, flexible and should have a sufficiently fast response time to track the pulsatile flow in the vessel. Both the cost and ease of use of the complete system needs to be considered as well to produce a commercially successful product. Presently available devices are not capable of simultaneously meeting these various requirements.